/*
 *                               POK header
 *
 * The following file is a part of the POK project. Any modification should
 * be made according to the POK licence. You CANNOT use this file or a part
 * of a file for your own project.
 *
 * For more information on the POK licence, please see our LICENCE FILE
 *
 * Please follow the coding guidelines described in doc/CODING_GUIDELINES
 *
 *                                      Copyright (c) 2007-2021 POK team
 */

/* @(#)s_rint.c 5.1 93/09/24 */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

#ifdef POK_NEEDS_LIBMATH

/*
 * rint(x)
 * Return x rounded to integral value according to the prevailing
 * rounding mode.
 * Method:
 *	Using floating addition.
 * Exception:
 *	Inexact flag raised if x not equal to rint(x).
 */

#include "math_private.h"
#include <libm.h>

static const double TWO52[2] = {
    4.50359962737049600000e+15,  /* 0x43300000, 0x00000000 */
    -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
};

double rint(double x) {
  int32_t i0, jj0, sx;
  uint32_t i, i1;
  double w, t;
  EXTRACT_WORDS(i0, i1, x);
  sx = (i0 >> 31) & 1;
  jj0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  if (jj0 < 20) {
    if (jj0 < 0) {
      if (((i0 & 0x7fffffff) | i1) == 0)
        return x;
      i1 |= (i0 & 0x0fffff);
      i0 &= 0xfffe0000;
      i0 |= ((i1 | -i1) >> 12) & 0x80000;
      SET_HIGH_WORD(x, i0);
      w = TWO52[sx] + x;
      t = w - TWO52[sx];
      GET_HIGH_WORD(i0, t);
      SET_HIGH_WORD(t, (i0 & 0x7fffffff) | (sx << 31));
      return t;
    } else {
      i = (0x000fffff) >> jj0;
      if (((i0 & i) | i1) == 0)
        return x; /* x is integral */
      i >>= 1;
      if (((i0 & i) | i1) != 0) {
        if (jj0 == 19)
          i1 = 0x40000000;
        else
          i0 = (i0 & (~i)) | ((0x20000) >> jj0);
      }
    }
  } else if (jj0 > 51) {
    if (jj0 == 0x400)
      return x + x; /* inf or NaN */
    else
      return x; /* x is integral */
  } else {
    i = ((uint32_t)(0xffffffff)) >> (jj0 - 20);
    if ((i1 & i) == 0)
      return x; /* x is integral */
    i >>= 1;
    if ((i1 & i) != 0)
      i1 = (i1 & (~i)) | ((0x40000000) >> (jj0 - 20));
  }
  INSERT_WORDS(x, i0, i1);
  w = TWO52[sx] + x;
  return w - TWO52[sx];
}

#endif
